I am looking for one of the above ..500pf variable to complete the 1928 QST published Hartley Oscillator transmitter.
If you can help please let me know.
A picture of the cap can be seen here at the very bottom of this page on my website:
https://members.shaw.ca/ve7sl/wanted.html
The caps are clearly stamped "NATIONAL DX" and are unique in that the connecting terminals are at the front and back rather than the more normal side position.
Thanks! Steve